diff mbox series

[v2,1/4] drm/format-helper: Add drm_fb_{xrgb8888,gray8}_to_mono_reversed()

Message ID 20220204134347.1187749-2-javierm@redhat.com (mailing list archive)
State Handled Elsewhere
Headers show
Series drm/tiny: Add driver for Solomon SSD1307 OLED displays | expand

Commit Message

Javier Martinez Canillas Feb. 4, 2022, 1:43 p.m. UTC
Add support to convert XR24 and 8-bit grayscale to reversed monochrome for
drivers that control monochromatic panels, that only have 1 bit per pixel.

The drm_fb_gray8_to_mono_reversed() helper was based on the function that
does the same in the drivers/gpu/drm/tiny/repaper.c driver.

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
---

(no changes since v1)

 drivers/gpu/drm/drm_format_helper.c | 80 +++++++++++++++++++++++++++++
 include/drm/drm_format_helper.h     |  7 +++
 2 files changed, 87 insertions(+)

Comments

Thomas Zimmermann Feb. 4, 2022, 3:52 p.m. UTC | #1
Hi

Am 04.02.22 um 14:43 schrieb Javier Martinez Canillas:
> Add support to convert XR24 and 8-bit grayscale to reversed monochrome for
> drivers that control monochromatic panels, that only have 1 bit per pixel.
> 
> The drm_fb_gray8_to_mono_reversed() helper was based on the function that
> does the same in the drivers/gpu/drm/tiny/repaper.c driver.
> 
> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
> ---
> 
> (no changes since v1)
> 
>   drivers/gpu/drm/drm_format_helper.c | 80 +++++++++++++++++++++++++++++
>   include/drm/drm_format_helper.h     |  7 +++
>   2 files changed, 87 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_format_helper.c b/drivers/gpu/drm/drm_format_helper.c
> index 0f28dd2bdd72..cdce4b7c25d9 100644
> --- a/drivers/gpu/drm/drm_format_helper.c
> +++ b/drivers/gpu/drm/drm_format_helper.c
> @@ -584,3 +584,83 @@ int drm_fb_blit_toio(void __iomem *dst, unsigned int dst_pitch, uint32_t dst_for
>   	return -EINVAL;
>   }
>   EXPORT_SYMBOL(drm_fb_blit_toio);
> +
> +static void drm_fb_gray8_to_mono_reversed_line(u8 *dst, const u8 *src, size_t pixels)
> +{
> +	unsigned int xb, i;
> +
> +	for (xb = 0; xb < pixels / 8; xb++) {

In practice, all mode widths are multiples of 8 because VGA mandated it. 
So it's ok-ish to assume this here. You should probably at least print a 
warning somewhere if (pixels % 8 != 0)


> +		u8 byte = 0x00;
> +
> +		for (i = 0; i < 8; i++) {
> +			int x = xb * 8 + i;
> +
> +			byte >>= 1;
> +			if (src[x] >> 7)
> +				byte |= BIT(7);
> +		}
> +		*dst++ = byte;
> +	}
> +}
> +
> +/**
> + * drm_fb_gray8_to_mono_reversed - Convert grayscale to reversed monochrome
> + * @dst: reversed monochrome destination buffer
> + * @dst_pitch: Number of bytes between two consecutive scanlines within dst
> + * @src: 8-bit grayscale source buffer
> + * @clip: Clip rectangle area to copy
> + *
> + * DRM doesn't have native monochrome or grayscale support.
> + * Such drivers can announce the commonly supported XR24 format to userspace
> + * and use drm_fb_xrgb8888_to_gray8() to convert to grayscale and then this
> + * helper function to convert to the native format.
> + */
> +void drm_fb_gray8_to_mono_reversed(void *dst, unsigned int dst_pitch, const void *src,
> +				   const struct drm_rect *clip)

There's a bug here. You want to pass in a drm_framebuffer as fourth 
argument.

> +{
> +
> +	size_t height = drm_rect_height(clip);
> +	size_t width = drm_rect_width(clip);
> +	unsigned int y;
> +	const u8 *gray8 = src;
> +	u8 *mono = dst;
> +
> +	if (!dst_pitch)
> +		dst_pitch = width;

The dst_pitch is given in bytes. You have to device by 8. Here would be 
a good place to warn if (width % 8 != 0).

> +
> +	for (y = 0; y < height; y++) {
> +		drm_fb_gray8_to_mono_reversed_line(mono, gray8, dst_pitch);
> +		mono += (dst_pitch / 8);

The dst_pitch is already given in bytes.

> +		gray8 += dst_pitch;

'gray8 += fb->pitches[0]' would be correct.

> +	}
> +}
> +
> +/**
> + * drm_fb_xrgb8888_to_mono_reversed - Convert XRGB8888 to reversed monochrome
> + * @dst: reversed monochrome destination buffer
> + * @dst_pitch: Number of bytes between two consecutive scanlines within dst
> + * @src: XRGB8888 source buffer
> + * @fb: DRM framebuffer
> + * @clip: Clip rectangle area to copy
> + *
> + * DRM doesn't have native monochrome support.
> + * Such drivers can announce the commonly supported XR24 format to userspace
> + * and use this function to convert to the native format.
> + *
> + * This function uses drm_fb_xrgb8888_to_gray8() to convert to grayscale and
> + * then the result is converted from grayscale to reversed monohrome.
> + */
> +void drm_fb_xrgb8888_to_mono_reversed(void *dst, unsigned int dst_pitch, const void *src,
> +				      const struct drm_framebuffer *fb,
> +				      const struct drm_rect *clip)
> +{
> +	if (WARN_ON(fb->format->format != DRM_FORMAT_XRGB8888))
> +		return;
> +
> +	if (!dst_pitch)
> +		dst_pitch = drm_rect_width(clip);
> +
> +	drm_fb_xrgb8888_to_gray8(dst, dst_pitch, src, fb, clip);
> +	drm_fb_gray8_to_mono_reversed(dst, dst_pitch, dst, fb, clip);

Converting from dst into dst can give incorrect results. At some point 
we probably want to add restrict qualifiers to these pointers, to help 
the compiler with optimizing.

A better approach here is to pull the per-line conversion from 
drm_fb_xrgb8888_to_gray8() into a separate helper and implement a 
line-by-line conversion here. something like this:

   drm_fb_xrgb8888_to_mono_reversed()
   {
     char *tmp = kmalloc(size of a single line of gray8)

     for (heigth) {
        drm_fb_xrgb8888_to_gray8_line(tmp, ..., src, ...);
        drm_fb_gray8_to_mono_reversed(dst, ..., tmp, ...);

        src += fb->pitches[0]
        dst += dst_pitch;
     }

     kfree(tmp);
   }

Best regards
Thomas

> +}
> +EXPORT_SYMBOL(drm_fb_xrgb8888_to_mono_reversed);
> diff --git a/include/drm/drm_format_helper.h b/include/drm/drm_format_helper.h
> index b30ed5de0a33..85e551a5cbe6 100644
> --- a/include/drm/drm_format_helper.h
> +++ b/include/drm/drm_format_helper.h
> @@ -43,4 +43,11 @@ int drm_fb_blit_toio(void __iomem *dst, unsigned int dst_pitch, uint32_t dst_for
>   		     const void *vmap, const struct drm_framebuffer *fb,
>   		     const struct drm_rect *rect);
>   
> +void drm_fb_gray8_to_mono_reversed(void *dst, unsigned int dst_pitch, const void *src,
> +				   const struct drm_rect *clip);
> +
> +void drm_fb_xrgb8888_to_mono_reversed(void *dst, unsigned int dst_pitch, const void *src,
> +				      const struct drm_framebuffer *fb,
> +				      const struct drm_rect *clip);
> +
>   #endif /* __LINUX_DRM_FORMAT_HELPER_H */
Thomas Zimmermann Feb. 4, 2022, 4 p.m. UTC | #2
Am 04.02.22 um 16:52 schrieb Thomas Zimmermann:
[...]
>> +/**
>> + * drm_fb_xrgb8888_to_mono_reversed - Convert XRGB8888 to reversed 
>> monochrome
>> + * @dst: reversed monochrome destination buffer
>> + * @dst_pitch: Number of bytes between two consecutive scanlines 
>> within dst
>> + * @src: XRGB8888 source buffer
>> + * @fb: DRM framebuffer
>> + * @clip: Clip rectangle area to copy
>> + *
>> + * DRM doesn't have native monochrome support.
>> + * Such drivers can announce the commonly supported XR24 format to 
>> userspace
>> + * and use this function to convert to the native format.
>> + *
>> + * This function uses drm_fb_xrgb8888_to_gray8() to convert to 
>> grayscale and
>> + * then the result is converted from grayscale to reversed monohrome.
>> + */
>> +void drm_fb_xrgb8888_to_mono_reversed(void *dst, unsigned int 
>> dst_pitch, const void *src,
>> +                      const struct drm_framebuffer *fb,
>> +                      const struct drm_rect *clip)
>> +{
>> +    if (WARN_ON(fb->format->format != DRM_FORMAT_XRGB8888))
>> +        return;
>> +
>> +    if (!dst_pitch)
>> +        dst_pitch = drm_rect_width(clip);
>> +
>> +    drm_fb_xrgb8888_to_gray8(dst, dst_pitch, src, fb, clip);
>> +    drm_fb_gray8_to_mono_reversed(dst, dst_pitch, dst, fb, clip);
> 
> Converting from dst into dst can give incorrect results. At some point 
> we probably want to add restrict qualifiers to these pointers, to help 
> the compiler with optimizing.
> 
> A better approach here is to pull the per-line conversion from 
> drm_fb_xrgb8888_to_gray8() into a separate helper and implement a 
> line-by-line conversion here. something like this:
> 
>    drm_fb_xrgb8888_to_mono_reversed()
>    {
>      char *tmp = kmalloc(size of a single line of gray8)
> 
>      for (heigth) {
>         drm_fb_xrgb8888_to_gray8_line(tmp, ..., src, ...);
>         drm_fb_gray8_to_mono_reversed(dst, ..., tmp, ...);

Here, I meant 'drm_fb_gray8_to_mono_reversed_line()'

> 
>         src += fb->pitches[0]
>         dst += dst_pitch;
>      }
> 
>      kfree(tmp);
>    }

To elaborate, this is an example of what I meant by composable. In the 
future, we can generalize this function and hand-in 2 function pointers 
the do the conversion with tmp as intermediate buffer. That would work 
for any combination of formats that have a common intermediate format.

> 
> Best regards
> Thomas
> 
>> +}
>> +EXPORT_SYMBOL(drm_fb_xrgb8888_to_mono_reversed);
>> diff --git a/include/drm/drm_format_helper.h 
>> b/include/drm/drm_format_helper.h
>> index b30ed5de0a33..85e551a5cbe6 100644
>> --- a/include/drm/drm_format_helper.h
>> +++ b/include/drm/drm_format_helper.h
>> @@ -43,4 +43,11 @@ int drm_fb_blit_toio(void __iomem *dst, unsigned 
>> int dst_pitch, uint32_t dst_for
>>                const void *vmap, const struct drm_framebuffer *fb,
>>                const struct drm_rect *rect);
>> +void drm_fb_gray8_to_mono_reversed(void *dst, unsigned int dst_pitch, 
>> const void *src,
>> +                   const struct drm_rect *clip);
>> +
>> +void drm_fb_xrgb8888_to_mono_reversed(void *dst, unsigned int 
>> dst_pitch, const void *src,
>> +                      const struct drm_framebuffer *fb,
>> +                      const struct drm_rect *clip);
>> +
>>   #endif /* __LINUX_DRM_FORMAT_HELPER_H */
>
Javier Martinez Canillas Feb. 4, 2022, 7:31 p.m. UTC | #3
Hello Thomas,

Thanks a lot for your feedback.

On 2/4/22 16:52, Thomas Zimmermann wrote:

[snip]

>> +static void drm_fb_gray8_to_mono_reversed_line(u8 *dst, const u8 *src, size_t pixels)
>> +{
>> +	unsigned int xb, i;
>> +
>> +	for (xb = 0; xb < pixels / 8; xb++) {
> 
> In practice, all mode widths are multiples of 8 because VGA mandated it. 
> So it's ok-ish to assume this here. You should probably at least print a 
> warning somewhere if (pixels % 8 != 0)
>

Agreed.
 
[snip]

>> + * DRM doesn't have native monochrome or grayscale support.
>> + * Such drivers can announce the commonly supported XR24 format to userspace
>> + * and use drm_fb_xrgb8888_to_gray8() to convert to grayscale and then this
>> + * helper function to convert to the native format.
>> + */
>> +void drm_fb_gray8_to_mono_reversed(void *dst, unsigned int dst_pitch, const void *src,
>> +				   const struct drm_rect *clip)
> 
> There's a bug here. You want to pass in a drm_framebuffer as fourth 
> argument.
>
>> +{
>> +
>> +	size_t height = drm_rect_height(clip);
>> +	size_t width = drm_rect_width(clip);
>> +	unsigned int y;
>> +	const u8 *gray8 = src;
>> +	u8 *mono = dst;
>> +
>> +	if (!dst_pitch)
>> +		dst_pitch = width;
> 
> The dst_pitch is given in bytes. You have to device by 8. Here would be 
> a good place to warn if (width % 8 != 0).
>

Ok.
 
>> +
>> +	for (y = 0; y < height; y++) {
>> +		drm_fb_gray8_to_mono_reversed_line(mono, gray8, dst_pitch);
>> +		mono += (dst_pitch / 8);
> 
> The dst_pitch is already given in bytes.
>

Yes, I know but for reversed mono we want only 1/8 of the width since we
are converting from 8 bits per pixel greyscale to 1 bit per pixel mono.

Or am I misunderstanding what you meant ?

>> +		gray8 += dst_pitch;
> 
> 'gray8 += fb->pitches[0]' would be correct.
>

Ok.
 
[snip]

>> + */
>> +void drm_fb_xrgb8888_to_mono_reversed(void *dst, unsigned int dst_pitch, const void *src,
>> +				      const struct drm_framebuffer *fb,
>> +				      const struct drm_rect *clip)
>> +{
>> +	if (WARN_ON(fb->format->format != DRM_FORMAT_XRGB8888))
>> +		return;
>> +
>> +	if (!dst_pitch)
>> +		dst_pitch = drm_rect_width(clip);
>> +
>> +	drm_fb_xrgb8888_to_gray8(dst, dst_pitch, src, fb, clip);
>> +	drm_fb_gray8_to_mono_reversed(dst, dst_pitch, dst, fb, clip);
> 
> Converting from dst into dst can give incorrect results. At some point 
> we probably want to add restrict qualifiers to these pointers, to help 
> the compiler with optimizing.
> 
> A better approach here is to pull the per-line conversion from 
> drm_fb_xrgb8888_to_gray8() into a separate helper and implement a 
> line-by-line conversion here. something like this:
> 
>    drm_fb_xrgb8888_to_mono_reversed()
>    {
>      char *tmp = kmalloc(size of a single line of gray8)
> 
>      for (heigth) {
>         drm_fb_xrgb8888_to_gray8_line(tmp, ..., src, ...);
>         drm_fb_gray8_to_mono_reversed(dst, ..., tmp, ...);
> 
>         src += fb->pitches[0]
>         dst += dst_pitch;
>      }
> 
>      kfree(tmp);
>    }
>

I see. Yes, that sounds a much better approach. I'll change it in v3.
 
Best regards,
Thomas Zimmermann Feb. 4, 2022, 8:35 p.m. UTC | #4
Hi

Am 04.02.22 um 20:31 schrieb Javier Martinez Canillas:
> Hello Thomas,
> 
> Thanks a lot for your feedback.
> 
> On 2/4/22 16:52, Thomas Zimmermann wrote:
> 
> [snip]
> 
>>> +static void drm_fb_gray8_to_mono_reversed_line(u8 *dst, const u8 *src, size_t pixels)
>>> +{
>>> +	unsigned int xb, i;
>>> +
>>> +	for (xb = 0; xb < pixels / 8; xb++) {
>>
>> In practice, all mode widths are multiples of 8 because VGA mandated it.
>> So it's ok-ish to assume this here. You should probably at least print a
>> warning somewhere if (pixels % 8 != 0)
>>
> 
> Agreed.

After sending the mail, I realized that some code copies only parts of 
the source around; specifically for damage handling. None of this is 
aligned to multiple of 8. So the copying could start and end in the 
middle of bytes. You'd need a pixel-offset value of some sort.

If you don't want to handle this now, maybe at least detect this case 
and put a warning somewhere.

>   
> [snip]
> 
>>> + * DRM doesn't have native monochrome or grayscale support.
>>> + * Such drivers can announce the commonly supported XR24 format to userspace
>>> + * and use drm_fb_xrgb8888_to_gray8() to convert to grayscale and then this
>>> + * helper function to convert to the native format.
>>> + */
>>> +void drm_fb_gray8_to_mono_reversed(void *dst, unsigned int dst_pitch, const void *src,
>>> +				   const struct drm_rect *clip)
>>
>> There's a bug here. You want to pass in a drm_framebuffer as fourth
>> argument.
>>
>>> +{
>>> +
>>> +	size_t height = drm_rect_height(clip);
>>> +	size_t width = drm_rect_width(clip);
>>> +	unsigned int y;
>>> +	const u8 *gray8 = src;
>>> +	u8 *mono = dst;
>>> +
>>> +	if (!dst_pitch)
>>> +		dst_pitch = width;
>>
>> The dst_pitch is given in bytes. You have to device by 8. Here would be
>> a good place to warn if (width % 8 != 0).
>>
> 
> Ok.
>   
>>> +
>>> +	for (y = 0; y < height; y++) {
>>> +		drm_fb_gray8_to_mono_reversed_line(mono, gray8, dst_pitch);
>>> +		mono += (dst_pitch / 8);
>>
>> The dst_pitch is already given in bytes.
>>
> 
> Yes, I know but for reversed mono we want only 1/8 of the width since we
> are converting from 8 bits per pixel greyscale to 1 bit per pixel mono.
> 
> Or am I misunderstanding what you meant ?

I mean that if there are 80 pixel on a scanline, the value of dst_pitch 
is already 10. These pitch values are always given in bytes.

Best regards
Thomas

> 
>>> +		gray8 += dst_pitch;
>>
>> 'gray8 += fb->pitches[0]' would be correct.
>>
> 
> Ok.
>   
> [snip]
> 
>>> + */
>>> +void drm_fb_xrgb8888_to_mono_reversed(void *dst, unsigned int dst_pitch, const void *src,
>>> +				      const struct drm_framebuffer *fb,
>>> +				      const struct drm_rect *clip)
>>> +{
>>> +	if (WARN_ON(fb->format->format != DRM_FORMAT_XRGB8888))
>>> +		return;
>>> +
>>> +	if (!dst_pitch)
>>> +		dst_pitch = drm_rect_width(clip);
>>> +
>>> +	drm_fb_xrgb8888_to_gray8(dst, dst_pitch, src, fb, clip);
>>> +	drm_fb_gray8_to_mono_reversed(dst, dst_pitch, dst, fb, clip);
>>
>> Converting from dst into dst can give incorrect results. At some point
>> we probably want to add restrict qualifiers to these pointers, to help
>> the compiler with optimizing.
>>
>> A better approach here is to pull the per-line conversion from
>> drm_fb_xrgb8888_to_gray8() into a separate helper and implement a
>> line-by-line conversion here. something like this:
>>
>>     drm_fb_xrgb8888_to_mono_reversed()
>>     {
>>       char *tmp = kmalloc(size of a single line of gray8)
>>
>>       for (heigth) {
>>          drm_fb_xrgb8888_to_gray8_line(tmp, ..., src, ...);
>>          drm_fb_gray8_to_mono_reversed(dst, ..., tmp, ...);
>>
>>          src += fb->pitches[0]
>>          dst += dst_pitch;
>>       }
>>
>>       kfree(tmp);
>>     }
>>
> 
> I see. Yes, that sounds a much better approach. I'll change it in v3.
>   
> Best regards,
Ilia Mirkin Feb. 4, 2022, 9:02 p.m. UTC | #5
On Fri, Feb 4, 2022 at 10:53 AM Thomas Zimmermann <tzimmermann@suse.de> wrote:
>
> Hi
>
> Am 04.02.22 um 14:43 schrieb Javier Martinez Canillas:
> > Add support to convert XR24 and 8-bit grayscale to reversed monochrome for
> > drivers that control monochromatic panels, that only have 1 bit per pixel.
> >
> > The drm_fb_gray8_to_mono_reversed() helper was based on the function that
> > does the same in the drivers/gpu/drm/tiny/repaper.c driver.
> >
> > Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
> > ---
> >
> > (no changes since v1)
> >
> >   drivers/gpu/drm/drm_format_helper.c | 80 +++++++++++++++++++++++++++++
> >   include/drm/drm_format_helper.h     |  7 +++
> >   2 files changed, 87 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/drm_format_helper.c b/drivers/gpu/drm/drm_format_helper.c
> > index 0f28dd2bdd72..cdce4b7c25d9 100644
> > --- a/drivers/gpu/drm/drm_format_helper.c
> > +++ b/drivers/gpu/drm/drm_format_helper.c
> > @@ -584,3 +584,83 @@ int drm_fb_blit_toio(void __iomem *dst, unsigned int dst_pitch, uint32_t dst_for
> >       return -EINVAL;
> >   }
> >   EXPORT_SYMBOL(drm_fb_blit_toio);
> > +
> > +static void drm_fb_gray8_to_mono_reversed_line(u8 *dst, const u8 *src, size_t pixels)
> > +{
> > +     unsigned int xb, i;
> > +
> > +     for (xb = 0; xb < pixels / 8; xb++) {
>
> In practice, all mode widths are multiples of 8 because VGA mandated it.
> So it's ok-ish to assume this here. You should probably at least print a
> warning somewhere if (pixels % 8 != 0)

Not sure if it's relevant, but 1366x768 was a fairly popular laptop
resolution. There's even a dedicated drm_mode_fixup_1366x768 in
drm_edid.c. (Would it have killed them to add 2 more horizontal
pixels? Apparently.)

Cheers,

  -ilia
Thomas Zimmermann Feb. 7, 2022, 12:44 p.m. UTC | #6
Hi

Am 04.02.22 um 22:02 schrieb Ilia Mirkin:
> On Fri, Feb 4, 2022 at 10:53 AM Thomas Zimmermann <tzimmermann@suse.de> wrote:
>>
>> Hi
>>
>> Am 04.02.22 um 14:43 schrieb Javier Martinez Canillas:
>>> Add support to convert XR24 and 8-bit grayscale to reversed monochrome for
>>> drivers that control monochromatic panels, that only have 1 bit per pixel.
>>>
>>> The drm_fb_gray8_to_mono_reversed() helper was based on the function that
>>> does the same in the drivers/gpu/drm/tiny/repaper.c driver.
>>>
>>> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
>>> ---
>>>
>>> (no changes since v1)
>>>
>>>    drivers/gpu/drm/drm_format_helper.c | 80 +++++++++++++++++++++++++++++
>>>    include/drm/drm_format_helper.h     |  7 +++
>>>    2 files changed, 87 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/drm_format_helper.c b/drivers/gpu/drm/drm_format_helper.c
>>> index 0f28dd2bdd72..cdce4b7c25d9 100644
>>> --- a/drivers/gpu/drm/drm_format_helper.c
>>> +++ b/drivers/gpu/drm/drm_format_helper.c
>>> @@ -584,3 +584,83 @@ int drm_fb_blit_toio(void __iomem *dst, unsigned int dst_pitch, uint32_t dst_for
>>>        return -EINVAL;
>>>    }
>>>    EXPORT_SYMBOL(drm_fb_blit_toio);
>>> +
>>> +static void drm_fb_gray8_to_mono_reversed_line(u8 *dst, const u8 *src, size_t pixels)
>>> +{
>>> +     unsigned int xb, i;
>>> +
>>> +     for (xb = 0; xb < pixels / 8; xb++) {
>>
>> In practice, all mode widths are multiples of 8 because VGA mandated it.
>> So it's ok-ish to assume this here. You should probably at least print a
>> warning somewhere if (pixels % 8 != 0)
> 
> Not sure if it's relevant, but 1366x768 was a fairly popular laptop
> resolution. There's even a dedicated drm_mode_fixup_1366x768 in
> drm_edid.c. (Would it have killed them to add 2 more horizontal
> pixels? Apparently.)

D'oh!

Do you know how the text console looks in this mode? Fonts still expect 
a multiple of 8.

Best regards
Thomas

> 
> Cheers,
> 
>    -ilia
diff mbox series

Patch

diff --git a/drivers/gpu/drm/drm_format_helper.c b/drivers/gpu/drm/drm_format_helper.c
index 0f28dd2bdd72..cdce4b7c25d9 100644
--- a/drivers/gpu/drm/drm_format_helper.c
+++ b/drivers/gpu/drm/drm_format_helper.c
@@ -584,3 +584,83 @@  int drm_fb_blit_toio(void __iomem *dst, unsigned int dst_pitch, uint32_t dst_for
 	return -EINVAL;
 }
 EXPORT_SYMBOL(drm_fb_blit_toio);
+
+static void drm_fb_gray8_to_mono_reversed_line(u8 *dst, const u8 *src, size_t pixels)
+{
+	unsigned int xb, i;
+
+	for (xb = 0; xb < pixels / 8; xb++) {
+		u8 byte = 0x00;
+
+		for (i = 0; i < 8; i++) {
+			int x = xb * 8 + i;
+
+			byte >>= 1;
+			if (src[x] >> 7)
+				byte |= BIT(7);
+		}
+		*dst++ = byte;
+	}
+}
+
+/**
+ * drm_fb_gray8_to_mono_reversed - Convert grayscale to reversed monochrome
+ * @dst: reversed monochrome destination buffer
+ * @dst_pitch: Number of bytes between two consecutive scanlines within dst
+ * @src: 8-bit grayscale source buffer
+ * @clip: Clip rectangle area to copy
+ *
+ * DRM doesn't have native monochrome or grayscale support.
+ * Such drivers can announce the commonly supported XR24 format to userspace
+ * and use drm_fb_xrgb8888_to_gray8() to convert to grayscale and then this
+ * helper function to convert to the native format.
+ */
+void drm_fb_gray8_to_mono_reversed(void *dst, unsigned int dst_pitch, const void *src,
+				   const struct drm_rect *clip)
+{
+
+	size_t height = drm_rect_height(clip);
+	size_t width = drm_rect_width(clip);
+	unsigned int y;
+	const u8 *gray8 = src;
+	u8 *mono = dst;
+
+	if (!dst_pitch)
+		dst_pitch = width;
+
+	for (y = 0; y < height; y++) {
+		drm_fb_gray8_to_mono_reversed_line(mono, gray8, dst_pitch);
+		mono += (dst_pitch / 8);
+		gray8 += dst_pitch;
+	}
+}
+
+/**
+ * drm_fb_xrgb8888_to_mono_reversed - Convert XRGB8888 to reversed monochrome
+ * @dst: reversed monochrome destination buffer
+ * @dst_pitch: Number of bytes between two consecutive scanlines within dst
+ * @src: XRGB8888 source buffer
+ * @fb: DRM framebuffer
+ * @clip: Clip rectangle area to copy
+ *
+ * DRM doesn't have native monochrome support.
+ * Such drivers can announce the commonly supported XR24 format to userspace
+ * and use this function to convert to the native format.
+ *
+ * This function uses drm_fb_xrgb8888_to_gray8() to convert to grayscale and
+ * then the result is converted from grayscale to reversed monohrome.
+ */
+void drm_fb_xrgb8888_to_mono_reversed(void *dst, unsigned int dst_pitch, const void *src,
+				      const struct drm_framebuffer *fb,
+				      const struct drm_rect *clip)
+{
+	if (WARN_ON(fb->format->format != DRM_FORMAT_XRGB8888))
+		return;
+
+	if (!dst_pitch)
+		dst_pitch = drm_rect_width(clip);
+
+	drm_fb_xrgb8888_to_gray8(dst, dst_pitch, src, fb, clip);
+	drm_fb_gray8_to_mono_reversed(dst, dst_pitch, dst, fb, clip);
+}
+EXPORT_SYMBOL(drm_fb_xrgb8888_to_mono_reversed);
diff --git a/include/drm/drm_format_helper.h b/include/drm/drm_format_helper.h
index b30ed5de0a33..85e551a5cbe6 100644
--- a/include/drm/drm_format_helper.h
+++ b/include/drm/drm_format_helper.h
@@ -43,4 +43,11 @@  int drm_fb_blit_toio(void __iomem *dst, unsigned int dst_pitch, uint32_t dst_for
 		     const void *vmap, const struct drm_framebuffer *fb,
 		     const struct drm_rect *rect);
 
+void drm_fb_gray8_to_mono_reversed(void *dst, unsigned int dst_pitch, const void *src,
+				   const struct drm_rect *clip);
+
+void drm_fb_xrgb8888_to_mono_reversed(void *dst, unsigned int dst_pitch, const void *src,
+				      const struct drm_framebuffer *fb,
+				      const struct drm_rect *clip);
+
 #endif /* __LINUX_DRM_FORMAT_HELPER_H */